It is currently 17 Nov 2017, 16:41

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A jar contains 16 marbles, of which 4 are red, 3 are blue, a

Author Message
TAGS:

### Hide Tags

Manager
Joined: 10 Feb 2011
Posts: 112

Kudos [?]: 370 [0], given: 10

A jar contains 16 marbles, of which 4 are red, 3 are blue, a [#permalink]

### Show Tags

14 Feb 2011, 17:24
4
This post was
BOOKMARKED
00:00

Difficulty:

(N/A)

Question Stats:

86% (00:47) correct 14% (00:07) wrong based on 96 sessions

### HideShow timer Statistics

A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow. If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue?

A. 3/64
B. 1/20
C. 1/16
D. 1/12
E. 1/8

Kudos [?]: 370 [0], given: 10

Math Expert
Joined: 02 Sep 2009
Posts: 42248

Kudos [?]: 132517 [3], given: 12324

Re: A jar contains 16 marbles, of which 4 are red, 3 are blue, a [#permalink]

### Show Tags

14 Feb 2011, 17:47
3
KUDOS
Expert's post
banksy wrote:
A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow. If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue?

A. 3/64
B. 1/20
C. 1/16
D. 1/12
E. 1/8

Note that we want the first marble selected to be red and the second marble selected to be blue.

P=4/16*3/15=1/20.

_________________

Kudos [?]: 132517 [3], given: 12324

Current Student
Status: Up again.
Joined: 31 Oct 2010
Posts: 526

Kudos [?]: 546 [1], given: 75

Concentration: Strategy, Operations
GMAT 1: 710 Q48 V40
GMAT 2: 740 Q49 V42
Re: A jar contains 16 marbles, of which 4 are red, 3 are blue, a [#permalink]

### Show Tags

17 Feb 2011, 11:19
1
KUDOS
banksy wrote:
A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow. If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue?

A. 3/64
B. 1/20
C. 1/16
D. 1/12
E. 1/8

Its an "and" question so think multiplication.

Let P{a}= P{1st marble is red}= $$\frac{4}{16}$$
P{B}=P{2nd marble is blue}=$$\frac{3}{15}$$

P{A}andp{B}=$$\frac{4}{16}*\frac{3}{15}= \frac{1}{20}$$

_________________

My GMAT debrief: http://gmatclub.com/forum/from-620-to-710-my-gmat-journey-114437.html

Kudos [?]: 546 [1], given: 75

Manager
Joined: 10 Feb 2011
Posts: 112

Kudos [?]: 370 [0], given: 10

Re: A jar contains 16 marbles, of which 4 are red, 3 are blue, a [#permalink]

### Show Tags

17 Feb 2011, 12:11
gmatpapa, if we have "and" so it is multiplication, and if "or" it means addition?

Kudos [?]: 370 [0], given: 10

Current Student
Status: Up again.
Joined: 31 Oct 2010
Posts: 526

Kudos [?]: 546 [1], given: 75

Concentration: Strategy, Operations
GMAT 1: 710 Q48 V40
GMAT 2: 740 Q49 V42
Re: A jar contains 16 marbles, of which 4 are red, 3 are blue, a [#permalink]

### Show Tags

17 Feb 2011, 12:39
1
KUDOS
banksy wrote:
gmatpapa, if we have "and" so it is multiplication, and if "or" it means addition?

When you are determining the probability of one event AND another event, multiply the two probabilities together. Add the probabilities if you are determining the probability of one event OR another another event.

Example. The probabilities of chip and dale scoring 700 on GMAT are 1/10 and 1/15 respectively. What is the probability that:

1. Both Chip AND Dale score a 700: Since this is an AND question, you multiply them together. Therefore,
P{both score 700}= $$\frac{1}{10}*\frac{1}{15}=\frac{1}{150}$$

2. Either Chip OR Dale scores a 700: P{Chip scores 700}+P{Dale scores 700}-P{both score 700}= $$\frac{1}{10}+\frac{1}{15}-\frac{1}{150}= \frac{12}{75}$$.
_________________

My GMAT debrief: http://gmatclub.com/forum/from-620-to-710-my-gmat-journey-114437.html

Kudos [?]: 546 [1], given: 75

Manager
Joined: 10 Feb 2011
Posts: 112

Kudos [?]: 370 [0], given: 10

Re: A jar contains 16 marbles, of which 4 are red, 3 are blue, a [#permalink]

### Show Tags

17 Feb 2011, 14:54
nice example=) thanks a lot)

Kudos [?]: 370 [0], given: 10

Manager
Joined: 31 May 2015
Posts: 70

Kudos [?]: 32 [0], given: 117

Re: A jar contains 16 marbles, of which 4 are red, 3 are blue, a [#permalink]

### Show Tags

28 May 2016, 03:35
Does anyone know how to use the counting method on this question. Thanks.
_________________

GMAT loosers are born not made !!!

Kudos [?]: 32 [0], given: 117

Re: A jar contains 16 marbles, of which 4 are red, 3 are blue, a   [#permalink] 28 May 2016, 03:35
Display posts from previous: Sort by